Support dual-stacked peers

http/query/query.go

@@ -121,38 +121,53 @@ func (q Query) RequestedPeerCount(fallback int) int {
 	return fallback
 }
 
+func getIPs(ipstr string, ipv4, ipv6 net.IP) (net.IP, net.IP, bool) {
+	if ip := net.ParseIP(ipstr); ip != nil {
+		newIPv4 := ip.To4()
+
+		if ipv4 == nil && newIPv4 != nil {
+			ipv4 = newIPv4
+		} else if ipv6 == nil && newIPv4 == nil {
+			ipv6 = ip
+		}
+	}
+
+	return ipv4, ipv6, ipv4 != nil && ipv6 != nil
+}
+
 // RequestedIP returns the requested IP address from a Query.
-func (q Query) RequestedIP(r *http.Request, allowSpoofing bool) (net.IP, error) {
+func (q Query) RequestedIP(r *http.Request, allowSpoofing bool) (ipv4, ipv6 net.IP, err error) {
+	var done bool
+
 	if allowSpoofing {
 		if ipstr, ok := q.Params["ip"]; ok {
-			if ip := net.ParseIP(ipstr); ip != nil {
-				return ip, nil
-			}
+			ipv4, ipv6, done = getIPs(ipstr, ipv4, ipv6)
 		}
 
 		if ipstr, ok := q.Params["ipv4"]; ok {
-			if ip := net.ParseIP(ipstr); ip != nil {
-				return ip, nil
+			if ipv4, ipv6, done = getIPs(ipstr, ipv4, ipv6); done {
+				return
 			}
 		}
 
 		if ipstr, ok := q.Params["ipv6"]; ok {
-			if ip := net.ParseIP(ipstr); ip != nil {
-				return ip, nil
+			if ipv4, ipv6, done = getIPs(ipstr, ipv4, ipv6); done {
+				return
 			}
 		}
 	}
 
 	if xRealIPs, ok := q.Params["x-real-ip"]; ok {
-		if ip := net.ParseIP(string(xRealIPs[0])); ip != nil {
-			return ip, nil
+		if ipv4, ipv6, done = getIPs(string(xRealIPs[0]), ipv4, ipv6); done {
+			return
 		}
 	}
 
 	if r.RemoteAddr == "" {
-		if ip := net.ParseIP("127.0.0.1"); ip != nil {
-			return ip, nil
+		if ipv4 == nil {
+			ipv4 = net.ParseIP("127.0.0.1")
 		}
+		return
 	}
 
 	portIndex := len(r.RemoteAddr) - 1
@@ -164,10 +179,13 @@ func (q Query) RequestedIP(r *http.Request, allowSpoofing bool) (net.IP, error)
 
 	if portIndex != -1 {
 		ipstr := r.RemoteAddr[0:portIndex]
-		if ip := net.ParseIP(ipstr); ip != nil {
-			return ip, nil
+		if ipv4, ipv6, done = getIPs(ipstr, ipv4, ipv6); done {
+			return
 		}
 	}
 
-	return nil, errors.New("failed to parse IP address")
+	if ipv4 == nil && ipv6 == nil {
+		err = errors.New("failed to parse IP address")
+	}
+	return
 }

http/tracker.go

@@ -35,7 +35,7 @@ func NewAnnounce(cfg *config.Config, r *http.Request, p httprouter.Params) (*mod
 		return nil, models.ErrMalformedRequest
 	}
 
-	ip, err := q.RequestedIP(r, cfg.AllowIPSpoofing)
+	ipv4, ipv6, err := q.RequestedIP(r, cfg.AllowIPSpoofing)
 	if err != nil {
 		return nil, models.ErrMalformedRequest
 	}
@@ -65,7 +65,8 @@ func NewAnnounce(cfg *config.Config, r *http.Request, p httprouter.Params) (*mod
 		Compact:    compact,
 		Downloaded: downloaded,
 		Event:      event,
-		IP:         ip,
+		IPv4:       ipv4,
+		IPv6:       ipv6,
 		Infohash:   infohash,
 		Left:       left,
 		NumWant:    numWant,

http/writer.go

@@ -70,17 +70,13 @@ func compactPeers(ipv6 bool, peers models.PeerList) []byte {
 
 	if ipv6 {
 		for _, peer := range peers {
-			if ip := peer.IP.To16(); ip != nil {
-				compactPeers.Write(ip)
-				compactPeers.Write([]byte{byte(peer.Port >> 8), byte(peer.Port & 0xff)})
-			}
+			compactPeers.Write(peer.IPv6)
+			compactPeers.Write([]byte{byte(peer.Port >> 8), byte(peer.Port & 0xff)})
 		}
 	} else {
 		for _, peer := range peers {
-			if ip := peer.IP.To4(); ip != nil {
-				compactPeers.Write(ip)
-				compactPeers.Write([]byte{byte(peer.Port >> 8), byte(peer.Port & 0xff)})
-			}
+			compactPeers.Write(peer.IPv4)
+			compactPeers.Write([]byte{byte(peer.Port >> 8), byte(peer.Port & 0xff)})
 		}
 	}
 
@@ -89,17 +85,25 @@ func compactPeers(ipv6 bool, peers models.PeerList) []byte {
 
 func peersList(ipv4s, ipv6s models.PeerList) (peers []bencode.Dict) {
 	for _, peer := range ipv4s {
-		peers = append(peers, peerDict(&peer))
+		peers = append(peers, peerDict(&peer, false))
 	}
 	for _, peer := range ipv6s {
-		peers = append(peers, peerDict(&peer))
+		peers = append(peers, peerDict(&peer, true))
 	}
 	return peers
 }
 
-func peerDict(peer *models.Peer) bencode.Dict {
+func peerDict(peer *models.Peer, ipv6 bool) bencode.Dict {
+	var ip string
+
+	if ipv6 {
+		ip = peer.IPv6.String()
+	} else {
+		ip = peer.IPv4.String()
+	}
+
 	return bencode.Dict{
-		"ip":      peer.IP.String(),
+		"ip":      ip,
 		"peer id": peer.ID,
 		"port":    peer.Port,
 	}